The present invention relates to a vehicle information communication technology including a vehicle-mounted equipment control technology using PLC (Power Line Communication) for transmitting a control signal as well as power by using a power line for feeding power to a load.
Power line communication (hereinafter referred to as PLC) is used as a communication method for controlling various types of electrical equipment mounted on an automobile such as a power window and a wiper.
FIG. 5 is a conceptual illustration showing a configuration of a vehicle-mounted equipment control system using PLC as an example of a vehicle information communication system. The system shown in FIG. 5 supplies power from a battery (not shown) to a plurality of loads 73 comprising electrical equipment, and a master controller 74 (hereinafter referred to simply as a master) and a slave controller 75 (hereinafter referred to simply as a slave) for controlling these loads via a junction connector (J/C) 72 connected to a power line 71. The slave 75 is a controller provided for each load 73 while the master 74 is a controller for controlling the loads 73 via the slaves 75. In this system, the master 74 transmits a communication signal SigM to the slave 75 as a distant party via a power line (a power line in the PLC network is hereinafter referred to as a sub power line) 77 in a PLC network 76 interconnected by the junction connector 72. The slave 75 receives the communication signal SigM via the sub power line 77 and transmits, via the sub power line 77, a communication signal SigS indicating the state of the load 73 controlled by the slave 75. The master 74 transmits a communication signal SigM corresponding to the communication signal SigS received from the slave 75. The master 74 and each slave 75 control the respective loads 72 while communicating with each other via the sub power line 76 (refer to JP-A-2003-118509).
A vehicle-mounted equipment control system using PLC is capable of performing proper control operation in case the PLC network exists alone as shown in FIG. 5, because communication between the master and the slaves are kept stable. FIG. 6 shows the case of two PLC networks 80 and 90 which are adjacent to each other via the main power line 71. As shown in FIG. 6, interference between the PLC networks 80 and 90 may cause improper control operation. In the example of FIG. 6, a communication signal SigA communicated between the master 83 and the slave 84 in the PLC network 80 invades, via the main power line 71, the PLC network 90 that is adjacent to the PLC network 80, thus interfering with the communication in the PLC network 90. Conversely, a communication signal SigB in the PLC network 90 invades the PLC network 80 via the main power line 71, thus interfering with the communication in the PLC network 80.